Description: (Abstract of the project) Central to the vectorial transport function of renal epithelium is the polarized distribution of surface membrane proteins in renal epithelial cells. Recent evidence indicates that the spectrin based cortical cytoskeleton, associated with many integral membrane proteins, is also highly polarized and may play a fundamental role in maintaining and guiding topographic membrane assembly. Recent evidence also indicates that a separate but related Golgi spectrin skeleton (SAATS) modulates the assembly and trafficking of certain membrane proteins such as Na,K-ATPase. The overall goal of the proposed studies will be to understand how the cortical and vesicular cytoskeletons achieve their polarized distribution, and the relationship of this process to the sorting of the basolateral integral membrane proteins Na,K-ATPase and E-cadherin. Specifically, research will focus on how perturbation of the factors that target spectrin to the lateral margins of kidney epithelial cells regulate its interactions with other integral membrane proteins such as E-cadherin and Na,K-ATPase, and how these processes affect in vivo renal development, function, and the response of the kidney to pathologic stress. Specific proteins to be examined include beta 1, beta II, and beta III spectrin, several isoforms of ankyrin including those associated with the vesicular Golgi spectrin skeleton (AnkG119), and a form of ankyrin associated with the nucleus. Also of interest are selected adapter proteins including alpha and beta-catenin. The interaction between these proteins will be measured by sensitive genetic and biochemical assays, and their role in vivo gauged by constructing transgenic and gene knock-out/knock-in mice with specific cytoskeletal mutations. In collaboration with other members of the program project team, the intersection of the spectrin based assembly pathways with other components of the epithelial and endothelial cell actin cytoskeleton and adhesion complexes will also be explored. As novel regulatory cascades involving the spectrin-ankyrin cortical and vesicular cytoskeletons are identified, the role of these cascades in mediating acute renal injury in vivo will be explored. It is anticipated that these studies will guide our search for renal diseases in which membrane cytoskeletal dysfunction plays an etiologic role, and will aid in designing rationale clinical responses to the cellular events that accompany acute renal hypoxic and anoxic injury.